Many industrial machines (e.g., locomotives, trucks, earth-moving equipment, windmills, and the like) include elements or assemblies (e.g., mechanical drive trains) that operate within difficult environments and/or endure substantial amounts of thermal or torsional stress as well as shock and vibration. It is often desirable to monitor a condition of an element or assembly so that it may be replaced or repaired before severe and permanent damage is sustained by the machine. Often, fluid lubricants are used to provide lubrication and cooling to increase performance of the machine and/or to increase the lifetime operation of the machine. Lubricants reduce the friction between two parts that engage each other and may also dissipate heat that is generated by the friction between the two parts. In addition to lubricants, fluids include other industrial fluid such as fuels, hydraulic media, drive fluids, power steering fluids, power brake fluids, drilling fluids, oils, insulating fluids, heat transfer fluids, or the like. Such fluids allow efficient and safe operation of machinery in transportation, industrial, locomotive, marine, automotive, construction, medical, and other applications. Fluids also include naturally occurring fluids such as oils, water, body fluids, biological fluids, and the like that occur in natural living and non-living systems.
The quality of a lubricant may decrease over time due to the introduction of contaminants and/or aging of the lubricant. Lubricants in a reservoir can become contaminated by contaminants such as water, metallic particles, and non-metallic particles. Contaminated fluids may lead to damaged parts or a decreased performance of the machine. Water is a common and destructive lubricant contaminant. The water may be introduced from a coolant leak, condensation from environmental exposure, equipment cleaning, and/or combustion. Water adversely affects the lubricant properties by increasing engine wear, causing corrosion, and accelerating oil oxidation. In addition, the lubricant may age due to repetitive thermal and viscous cycles resulting in the loss of fluid properties such as viscosity as the lubricant chemically breaks down. Furthermore, stabilizing additives that are added to the lubricants to provide increased resilience within harsh environments, such as high temperatures, may begin to break down. The reduction in additive concentration provides less thermal stability for the lubricant, causing the lubricant to degrade faster over time. As the additive is depleted, acidic components, such as by-products from the degradation of the oil or additive, may be introduced into the lubricant fluid. The acidic components are contaminants that reduce the effectiveness or performance of the lubricant. Typical combustion engines (reciprocating & rotating turbine) during the combustion process create acidic by-products such as oxides of nitrogen and oxides of sulfur which enter the lubricating oil in the power cylinder or power turbine. These acidic components deplete the basic additives that are present in the lubricating oil during the life of the engine.
Conventional methods of inspecting fluids of a machine include visual inspection of the fluid (e.g., dipsticks) or a sensor that is directly wired to a system. These methods may not be practical and/or may have limited capabilities. For example, due to the configuration of some machines, it may be difficult to visually inspect the fluid. Also, hardwired sensors may not be suitable for machines that frequently move and/or are exposed to harsh conditions.
Robust sensing of fluids may be useful in mobile and stationary equipment applications. As an example, if the equipment is a vehicle engine and the fluid is engine oil, then knowledge about oil health may be used to help reduce or prevent unexpected downtime, provide savings from unnecessary oil replacement, and improve service intervals scheduling in vehicles such as locomotives, heavy and light duty trucks; mining, construction, and agriculture vehicles. Other examples of stationary equipment applications may include wind turbines and gensets. Further, knowledge about engine oil health may prevent or reduce the total life cost of passenger cars, improve control of service intervals, and extend the life of engine.
Standard (classic) impedance spectroscopy is a technique that is employed to characterize aspects of material performance. In classic impedance spectroscopy, a material may be positioned between electrodes and probed over a wide frequency range (from a fraction of Hz to tens of GHz) to extract the fundamental information about dielectric properties of the material. Standard impedance spectroscopy may be limited due to its low sensitivity in reported measurement configurations and prohibitively long acquisition times over the broad frequency range. Therefore, standard impedance spectroscopy is difficult to perform in the field.
It may be desirable to have systems and methods for in-situ monitoring of fluid properties that differ from those systems and methods that are currently available.